Contact Lenses With Blended Microchannels

ABSTRACT

Contact lenses for use in eyes are provided and include a lens body and a plurality of microchannels defined in a posterior face of the lens body. The microchannels are structured to promote effective tear fluid exchange between an exposed surface of the eye and a surface of the eye covered by the lens body. Each of the microchannels preferably includes a substantially junctionless, convex surface along a major portion of a length of the microchannel.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/055,884, filed Feb. 11, 2005, which is a continuation of U.S. patentapplication Ser. No. 10/337,247, filed Jan. 6, 2003, which is acontinuation-in-part of U.S. patent application Ser. No. 10/270,025,filed Oct. 11, 2002, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/910,355, filed Jul. 20, 2001, which claims thebenefit of U.S. provisional application Ser. No. 60/221,575, filed Jul.28, 2000, the disclosures of each of these applications beingincorporated in their entirety herein by this specific reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to contact lenses and morespecifically relates to contact lenses having microchannels that promoteeffective tear fluid exchange.

It has long been recognized that extended wear of contact lenses canlead to corneal complications. Adverse corneal responses to extendedcontact lens wear are believed to be primarily caused by accumulation ofdebris trapped at the lens-eye interface.

The cornea is a living tissue with an active metabolism. Waste products,for example lactic acid, carbon dioxide and water, generated by suchmetabolism must be expelled from the cornea. Contact lens wear resultsin debris, for example, derived from such waste products, deadepithelial cells, and other materials which are ordinarily removed fromthe eye, becoming trapped at the lens-eye interface. Such debris, ifleft to accumulate in the eye, can harm the eye, for example, causingirritation and/or other harm to the eye and/or to the general ocularhealth of the lens wearer. In order to remain healthy, the cornea mustreceive an adequate supply of oxygen as the cornea does not receiveoxygen from the blood supply as does other living tissue. If sufficientoxygen does not reach the cornea, corneal swelling occurs.

In order to address the problem of oxygen deprivation due to extendedwear of contact lenses, hydrophilic lenses with high oxygen transmissionproperties were developed. Hydrophilic lenses, also sometimes referredto as hydrogel lenses, are soft, flexible, water-containing lenses.Clinical studies of hydrophilic lenses have indeed shown a relativelylower degree of corneal swelling in persons wearing such lenses, evenwhen worn over an extended time.

Unfortunately, however, the use of conventional hydrophilic lenses havenot eliminated all adverse corneal responses to contact lens wear, inparticular extended contact lens wear. For example, conventionalhydrophilic lenses do not address the problem of debris accumulation atthe lens-eye interface. This suggests that in addition to oxygenpermeability, there are other considerations to be addressed in thedevelopment of a safe, soft contact lens for extended wear.

One important consideration is effective tear film exchange between theexposed surface of the eye and the surface of the eye covered by thelens. Tear fluids provide for hydration of delicate eye tissue andcontinuous flushing of debris from the eye. Tear film exchange betweenthe eye and the posterior, i.e. eye facing, surface of a contact lens,is believed to be a critical factor in maintaining eye health. Tear filmexchange allows for removal of dead epithelial cells, foreignparticulate matter and other debris that may otherwise become trappedbetween the lens and the eye. It has been hypothesized that increasedtear film exchange will not only enhance corneal health but will limitcomplications such as infection in the eye and microbial keratitis.

Rotation of the lens on the eye has long been recognized as a means ofmaintaining eye health and comfort. For example, Gordon U.S. Pat. No.2,989,894 describes a contact lens having five equally spaced, spirallyinclined ducts formed on an inner surface of the lens. Each duct isdescribed and shown as extending toward a center of the lens but withoutextending as far as the corneal region. It is stated that the slow andconstant rotation of the lens prevents excess settling of the lens onthe cornea. The spiral inclination of the ducts is said to cause thelens to rotate in a clockwise or counterclockwise direction dependingupon the direction of inclination.

More recently, Höfer et al U.S. Pat. No. 5,166,710 discloses a contactlens having a corneal region that, when placed on the eye, is spacedapart from the corneal surface. Provision is made for causing the lensto rotate upon eyelid blinking action of the wearer. According to Höferet al, lacrimal film is transported along the eye surface as a result ofa “turbo effect” produced by flattened zones on the lens, which causesthe lens to rotate on the eye in response to blinking action. The patentalso describes that tear transport may be provided by depressions in therear face of the lens body. Höfer et al shows and describes that thedepressions may be depressed portions of the lens body, within the rearsurface thereof, the depressions being groove-like or saw tooth-like inshape. Höfer et al describes that it is also possible to provide “thinwave-like curved channels”.

Nicolson et al U.S. Pat. 5No. 5,849,811 discloses a lens material thatwas developed to provide a balance of oxygen permeability with ion orwater permeability, with the permeability being sufficient to providecontact lens “eye-on movement”, i.e. movement of the lens on the eyesurface.

The disclosure of each of the patents identified herein is herebyincorporated in its entirety herein by this specific reference.

Despite the advances made in development of comfortable, safe, extendedwear contact lenses, there is still a need for an improved contact lens,for example, a lens that promotes effective tear fluid exchangethroughout the surface area of the eye, particularly in the area of thecornea.

SUMMARY OF THE INVENTION

New contact lenses effective to promote effective tear fluid exchangebetween an exposed surface of an eye and a surface of an eye covered bythe contact lens have been discovered. Exchange of tear fluid or filmfrom outside the periphery of the lens with tear fluid or film disposedbehind the lens, that is between the lens and the eye or at the lens-eyeinterface, provides for enhanced removal of debris from the lens-eyeinterface. The tear film located between the cornea and a contact lensis sometimes referred to herein as the post-lens tear film (PoLTF).Consistent flushing of the PoLTF can result in enhanced ocular healthand/or long periods of extended contact lens wear with reduced adversecorneal responses.

Contact lenses, for example, extended wear contact lenses, in accordancewith the present invention, provide for removal of debris from beneaththe contact lens through enhanced tear mixing, for example by consistentflushing of the PoLTF; preferably provide increased delivery of oxygento the cornea; and preferably do not depend upon rotation of the lensfor promoting the effectiveness of tear fluid or film exchange.

In one broad aspect of the present invention, a contact lens is providedwhich generally comprises a lens body having a posterior face and ananterior face. A plurality of microchannels are defined in the posteriorface, and the lens body is structured to reduce the time to exchange 95%of tear fluid, for example, from the PoLTF, such as by at least about15%, when the lens is worn on the eye, relative to a substantiallyidentical contact lens that does not include, or is without, a pluralityof microchannels. In another aspect of the invention, the lens body,preferably including a plurality of microchannels, as described herein,is structured to cause the lens body to flex toward the eye wearing thecontact lens in response to the action of an eyelid on the lens body,thereby at least assisting in promoting effective tear fluid exchangebetween an exposed surface of the eye and a surface of the eye coveredby the lens body and preferably to reduce the time to exchange 95% oftear fluid by at least about 15% when the lens is worn on the eye,relative to a substantially identical contact lens that does not soflex.

Without wishing to limit the invention to any particular theory ofoperation, it is believed that the structure of the lens body, forexample in response to a blinking action of the eyelid, is believed tocause the lens to produce a significant pumping or flushing action oftear fluid between the lens and an eye surface covered by the lens. Moreparticularly, in accordance with this aspect of the invention, uponclosing of the eyelid, for example during a blinking action, the eyelidpushes the lens closer to the cornea, which squeezes some of the PoLTFout from beneath the lens. Upon the eyelid being subsequently raised,the elasticity of the lens causes the lens to recoil and move away fromthe cornea thereby drawing tear fluid from the tear film on thesurrounding sclera, and effectively replenishing the PoLTF.

In a particular embodiment of the invention, the lens body preferablyhas a thickness which varies substantially continuously along a radiusextending from an optical axis of the lens body circumferentially acrossat least a portion of each of the microchannels.

For example, the plurality of microchannels defines a waveform,circumferentially. More preferably, the plurality of microchannelsdefines a substantially continuous, preferably substantiallyjunctionless waveform. Stated another way, the plurality ofmicrochannels preferably defines substantially smooth, substantiallycontinuously curved surfaces, generally extending from an optic of thelens across a peripheral portion of the lens body.

Preferably, each of the microchannels has a width in a range of about 5degrees and about 30 degrees (for example, in a 360 degree substantiallycircular array). The plurality of microchannels may comprise betweenabout 3 to about 200 microchannels, more preferably about 10 to about100 microchannels.

In one embodiment of the invention, the lens includes an optical zonewhich is substantially free of the plurality of microchannels. Forexample, the plurality of microchannels may be defined only in aperipheral portion of the lens.

Preferably, each of the microchannels includes a curved surface that isother than convex relative to the anterior face of the lens body. Morepreferably, each microchannel is substantially continuously curved bothradially and circumferentially, wherein “circumferentially” is definedherein as being along at least one radius extending from an optical axisof the lens body.

In a particularly useful embodiment of the invention, at least twomicrochannels define a waveform circumferentially. As used herein, awaveform is a continuous curve including an apex of each of at least twomicrochannels. In this context, an apex of a microchannel is theposterior most point of the microchannel. Even more preferably, theplurality of microchannels defines a substantially continuous waveformcircumferentially, still more preferably a substantially continuous,substantially junctionless waveform circumferentially, generally havingtroughs at the thinnest region of the lens body and peaks at thethickest region of the lens body. In a more specific aspect of theinvention, the waveform repeats periodically about at least a portion ofthe circumference of the lens.

In another broad aspect of the invention, a contact lens is providedcomprising a lens body having a posterior face and an anterior face, andthe lens body includes a plurality of microchannels, each microchannelincluding a curved surface that is generally other than concave,preferably that is generally convex, to the anterior face of the lensbody. Preferably, the curved surface of each microchannel is located ina posterior region of the microchannel.

In one embodiment, the lens body may have a thickness which variessubstantially continuously along a radius extending from an optical axisof the lens body across at least a portion, for example, a majorportion, or substantially all of each of the microchannelscircumferentially. In one embodiment, the lens body has a thicknesswhich varies substantially continuously along a radius extending fromthe optical axis across only a portion of each of the microchannelscircumferentially.

Preferably, each of the microchannels is substantially smooth orjunctionless and continuously curved both radially andcircumferentially.

Preferably, each of the microchannels has a decreasing taper toward anoptical axis of the lens body, in terms of at least one of a width and adepth of the microchannels.

In one embodiment of the invention, the lens includes an optical zonewhich is substantially free of the plurality of microchannels. Forexample, the plurality of microchannels may be defined only in aperipheral portion of the lens.

Again, without wishing to limit the invention to any particular theoryof operation, it is believed that the generally non-concave curvedsurfaces of the microchannels are effective in enhancing the tear fluidexchange, for example by at least about 15%, preferably to at leastabout 35% or more, as described herein, relative to a substantiallyidentical contact lens without microchannels or including microchannelswithout such curved surfaces.

When using a T₉₅ test, as described herein, the present contact lensesare structured to reduce the time to exchange 95% of tear fluid by atleast about 15% or at least about 20% or at least about 25% or at leastabout 30% or at least about 35% or more when the lens is worn on the eyecompared to a reference contact lens, for example, a substantiallyidentical contact lens without microchannels, or without microchannelsin accordance with the present invention.

In another broad aspect of the invention, a contact lens is providedthat generally comprises a lens body and a plurality of microchannelsdefined in the posterior face of the lens body, with each of themicrochannels being located in a substantially abutting relationship toone or more of the microchannels. The microchannels are preferably sizedand adapted to promote effective, and more preferably to enhance, tearfluid exchange between an exposed surface of the eye and a surface ofthe eye covered by the lens body.

Each of the microchannels, for example, abutting microchannels, arepreferably sized and/or shaped such as to define a significant openspacing between the posterior face of the lens body and an eye surfacewhen the lens is worn on the eye. For example, the plurality ofmicrochannels may occupy a substantial portion of the posterior face,thereby creating a consistent PoLTF between the eye surface and thelens. For example, in accordance with the present invention, theplurality of microchannels may occupy at least about 10% or about 20% toabout 30% or about 50% or more of the portion of the posterior face onwhich the microchannels are located. Preferably, the contact lens isstructured to cause the lens body to flex toward and away from the eyewearing the contact lens in response to the action of an eyelid comingin contact with, and moving away from the lens body, respectively,thereby at least assisting in promoting effective tear fluid exchangebetween an exposed surface of the eye and a surface of the eye coveredby the lens body.

Each abutting microchannel may include a curved surface that isgenerally other than concave relative to the anterior face of the lensbody. For example, each microchannel may include a curved surface thatis generally convex relative to the anterior face of the lens body.

Preferably, the contact lenses of the present invention are produced bylathing techniques. More particularly, the plurality of microchannelsare preferably lathed on a tooling insert that is used to form a contactlens mold.

Alternatively, the microchannels in the present contact lenses can beprovided using any suitable technique or processing or combinationsthereof. Preferably, such microchannels are provided during contact lensmanufacture using techniques which are conventional and well known inthe art. For example, there are at least three opportunities in theprocess of making contact lens that microchannels can be imparted. Theseare as follows:

-   -   Etching or lathing (preferred) the molding insert using        techniques such as chemical, laser, EDM, photolithograph, UV        irradiation, micro-machining and the like;    -   building a relief on a thermoplastic mold using techniques such        as microcontact printing and the like; and    -   imparting the microchannels directly on a lens, such as by        lasing and the like.

It can be appreciated that when the lens of the present invention isworn for an extended period of time, the tear film at the lens/eyeinterface is continually flushed with tear fluid from other parts of theeye outside the lens periphery. This flushing of the tear film from thelens-eye interface, which often contains a substantial amount of debris,with “clean” tear film reduces the debris concentration and therebyallows the lens to be worn for a longer period of time before removalfrom the eye. Even if the lens is not worn for an extended period oftime, the continual flushing of the tear film has a significantlyadvantageous effect on the ocular health of the lens wearer.

Enhanced debris removal in accordance with the present invention isparticularly useful in combination with contact lenses having highoxygen permeability, such as hydrophilic contact lenses, for example,contact lenses made of hydrophilic polymeric materials, siliconehydrogel materials and the like.

Each and every feature described herein, and each and every combinationof two or more of such features, is included within the scope of thepresent invention provided that the features included in such acombination are not mutually inconsistent.

These and other aspects of the present invention are set forth in thefollowing detailed description, examples and claims, particularly whenconsidered in conjunction with the accompanying drawings in which likeparts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a contact lens in accordance with thepresent invention, the contact lens including a plurality ofmicrochannels defined in a posterior face of the lens.

FIG. 2 is a cross sectional view taken generally along line 2-2 of FIG.1.

FIG. 3 is a schematic view of the microchannel configuration of the lensshown in FIG. 1.

FIG. 4 is a plan view of the posterior face of the contact lens shown inFIG. 1.

FIG. 5 is a plan view of a posterior face of another embodiment of acontact lens in accordance with the present invention.

FIG. 6 is a perspective view of another contact lens in accordance withthe present invention.

FIG. 7 is a cross sectional view taken generally along line 7-7 of FIG.6.

FIG. 8 is a schematic view of the microchannel configuration of the lensshown in FIG. 6.

FIG. 8A is a schematic view of an alternative microchannel configurationof a contact lens of the present invention.

DETAILED DESCRIPTION

Turning now to FIGS. 1 and 2, a contact lens 10 in accordance with theinvention is shown. Contact lens 10 includes a lens body 14 with aposterior face 16 and an opposing anterior face 17 (not visible in FIG.1). The posterior face 16 includes an optical zone 18 configured forvision correction, and a peripheral portion 22 generally surrounding theoptical zone 18, and a peripheral edge surface 24. The posterior face16, as used herein, refers to the surface of the lens 10 which facestoward the eye during wear.

The lens 10 of the present invention generally comprises a plurality ofmicrochannels 30 defined in the posterior face 16. Generally, the lensbody 14 is structured to cause the lens body 14 to flex toward the eyewearing the contact lens 10, generally in a direction represented byarrows 28, in response to an action of the eyelid on the lens body 14,thereby at least assisting in promoting effective tear fluid exchange,for example by consistently replenishing the PoLTF, as describedelsewhere herein.

Advantageously, the microchannels 30 are preferably sized and adapted topromote effective tear fluid exchange between an exposed surface of theeye and a surface of the eye covered by the lens body 14.

Preferably, the present lenses are structured to increase tear mixing byat least about 15%, or at least about 20%, or at least about 25%, or atleast about 30%, or at least about 35% or more when the lens is worn onthe eye relative to an identical contact lens that does not includemicrochannels or that does not include microchannels structured asdescribed and shown herein. For example, the present contact lensespreferably include a lens body structured to reduce the time required toexchange 95% of the tear fluid by at least about 15%, or at least about20%, or at least about 25%, or at least about 30%, or at least about 35%or more when the contact lens is worn on an eye (for example, a humaneye) relative to a substantially identical contact lens withoutmicrochannels or without microchannels structured in accordance with thepresent invention. As described herein, the present lenses provideenhanced tear exchange rates ranging from about 0.4% enhancement to atleast 46% enhancement.

Each of the microchannels 30 preferably includes a curved surface 34,generally other than concave relative to the anterior face 17. Morespecifically, the curved surface 34 is generally convex relative to theanterior face 17 and is located in a posterior region of themicrochannel 30.

This may be more clearly understood with reference to FIG. 3. FIG. 3represents a cross section of the lens 10 along a portion of aparticular radial distance from an optical axis of the lens body. Forexample, FIG. 3 may represent a thickness of the lens 10 at a radius ordistance of about 4 mm from the optical axis of the lens body 14. Eachmicrochannel, for example 30′, is defined between apex 31 a and apex 31b.

Preferably, as shown in FIG. 1, the curved surface 34 of eachmicrochannel 30 is substantially continuously curved circumferentially.The lens body 14 therefor may be described as having a thickness whichvaries substantially continuously along a radius extending from theoptical axis of lens body 14 across adjacent, abutting microchannels,for example, microchannels 30′ and 30″ in FIG. 3, with thickest portionsbeing at apexes 31 a and 31 b. It should be noted that each apex 31 aand 31 b is an apex of two microchannels. For example, apex 31 b iscommon to both microchannels 30′ and 30″.

Preferably, each microchannel is located in a substantially abuttingrelationship to one or more adjacent microchannels. For example, thecurved surface of a particular microchannel is located in asubstantially abutting relationship to a curved surface of one or moreother microchannels. The plurality of microchannels 30 preferablydefines a continuous, junctionless curved surface on at least a portionof the posterior face 16 of the lens 10. The present lenses, forexample, such lenses which have at least partially junctionlessmicrochannels, provide substantial wearer comfort benefits, for example,relative to contact lenses including microchannels, such as spaced apartmicrochannels, with junctions or discontinuities (discontinuous or sharpedges).

More preferably, the plurality of microchannels 30 define a waveformcircumferentially. A waveform is defined herein as a continuous curveincluding an apex of at least two microchannels. Preferably, thewaveform is a substantially continuous waveform. Even more preferably,the plurality of microchannels defines a substantially junctionlesswaveform. For example, each microchannel is preferably substantiallyjunctionless along at least a portion of, preferably a major portion of,a length of the microchannel.

For example, in the embodiment shown in FIG. 1, the plurality ofmicrochannels defines a continuous waveform, radiating from the opticalzane 18 and extending across at least a portion of the peripheralportion 22 of the lens body 14. Preferably, the microchannels 30 aresubstantially smooth and continuously curved both radially andcircumferentially. The waveform defined by the plurality ofmicrochannels may be periodic, such as shown in FIG. 1. In other words,the microchannels may be substantially equidistant from apex to apex,though this is not necessarily so.

The thinnest region of the lens body 14 within each microchannel 30 mayextend through about 5% or about 10% to about 30% or about 50% or about80% of the maximum thickness of the lens body 14. Each microchannel 30preferably has a decreasing taper toward the optical axis in terms ofwidth from the peripheral edge 24 of the lens, toward the optical zone18. Looked at from a different perspective, each microchannel 30preferably has a maximum width, for example at about the periphery 24 ofthe lens.

The contact lens 10 is structured to promote tear fluid exchange betweenan exposed surface of the eye and a surface of the eye covered by thelens 10. The microchannels 30 are effective to promote or facilitatesuch tear fluid exchange and preferably create a substantially freeflowing tear film in the lens eye interface. Moreover, the lens isstructured to cause a flushing of at least some of the PoLTF upon eachblink of the eye.

The plurality of microchannels 30 may include microchannels that have adepth dependent upon the thickness of the lens 10 itself. For example,each microchannel may have a depth of between about 0.1% to about 90% ofa thickness of the particular lens body. In one embodiment, eachmicrochannel has a depth of between about 10% and about 80% of athickness of the lens body. For typical contact lens thicknesses, themicrochannels in accordance with the invention have a depth of betweenabout 0.1 micron and about 50 microns.

In the embodiment shown in FIG. 1, the plurality of microchannels 30extend only into the peripheral portion 16 of the lens 10 and there isan absence of microchannels 30 in the optical zone 18. A junction ordiscontinuity may be present at the interface between the optical zoneand each microchannel. Except for this junction, each of themicrochannels preferably is completely junctionless. The plurality ofmicrochannels 30 extend at least a portion of the posterior face 16 fromthe optical zane 18 to the lens periphery 24 preferably to the periphery24. The absence of microchannels in the optical zone 18 reduces, or evensubstantially eliminates any detrimental effects that the microchannels30 may have on the vision quality or optical zone function provided bycontact lens 10.

In order to provide effective tear fluid exchange at the optical zone 18in the absence of microchannels, the contact lens 10 may be structuredsuch that the optical zane 18 of the lens 10 is somewhat anteriorlydisposed relative to the surrounding peripheral portion 22, specificallyrelative to the part or surface of peripheral portion 22 located betweenthe microchannels 30.

Although not specifically shown, as an alternative to microchannelshaving a relatively constant depth, each microchannel 30 may becomeincreasingly more shallow (less deep) from the peripheral edge 24 towardthe optical zone 18. Furthermore, the optical zane 18 may be anteriorlydisposed a distance substantially equal to the depth of the most shallowportion of the microchannel 30. For example, the optical zone may beanteriorly disposed about 20 microns or about 10 microns or about 5microns or less, relative to the peripheral portion 22.

FIG. 4 shows a plan view of the posterior face of the contact lens 10shown in FIG. 1. In this view, each solid radially extending line (forexample lines 50) represents a theoretical line where a curvature of theposterior surface 16 changes from a convex curve to a curve that isother than convex. In other words, lines 50 represent lines ofinflection where the lens posterior surface changes from concave toconvex. One microchannel 30 is defined as spanning an area A defined,for example, between dashed line 50 a and dashed line 50 b. In thisparticular embodiment 10, the plurality of microchannels 30 comprisestwelve microchannels, wherein each microchannel 30 occupies an areaspanning a width of about 30 degrees of the lens.

Preferably, the plurality of microchannels comprises about 3 to about192 or about 200 microchannels, for example, the plurality ofmicrochannels comprises about 5 or about 10 to about 100 microchannels.For example, FIG. 5 shows a similar contact lens 110 in accordance withthe present invention wherein the plurality of microchannels comprises24 microchannels, with each microchannel occupying about 15 degrees ofthe lens 110. Unless stated otherwise herein, the lens 110 of FIG. 5 isstructured and functions similarly to contact lens 10 of FIG. 1.

Turning now to FIGS. 6 and 7, another embodiment 210 of the invention isshown. Except as expressly described, contact lens 210 is structured andfunctions similar to contact lens 10. Components of lens 210 whichcorrespond to components of lens 10 are identified by the same referencenumeral increased by 200.

One of the primary differences between contact lens 210 and contact lens10 relates to the structure of the microchannels 230. Specifically, themicrochannels 230 each include a posterior portion defining a convexlycurved surface 234 and a portion 240 that is not defined by a curvedsurface. This may be more clearly understood with reference to FIG. 8which shows a schematic representation of lens 210 similar to FIG. 3. Asshown, each microchannel 230 is defined between apexes, for example 230a, and 230 b. The lens 210 therefore has a varying thickness at aparticular radial distance from the lens optic center or central opticalaxis. However, in addition to curved surfaces 234, each microchannel 230includes relatively flattened region 240. As shown, the flattened region240 is at the thinner region of the lens body 214 whereas the curvedsurfaces 234 are at the thicker region of the lens body 214.

FIG. 8A shows another contact lens 310 in accordance with the presentinvention, similar to lens 210. Except as expressly described, contactlens 310 is structured and functions similar to contact lens 210.Components of lens 310 which correspond to components of lens 10 areidentified by the same reference numeral increased by 300.

The primary difference between lens 310 and lens 210 relates to a largersurface area of each flattened region 340. This illustrates that thepresent contact lenses can have a wide variety of differently sized,shaped and configured microchannels and still be within the scope of thepresent invention.

In another aspect of the present invention, contact lenses are provided,which comprise lens bodies structured to provide enhanced tear mixing toone or more particular groups of individuals, for example, individualswith particular eye and/or eyelid anatomical and physiological features.Advantageously, the present contact lenses include lens bodiesstructured to provide enhanced tear mixing to individuals who haveincreased eyelid tension relative to other individuals who have areduced degree of, or less, eyelid tension. In one embodiment, contactlenses are structured to provide enhanced tear mixing for an Asianperson, as compared to a non-Asian person. In general, it is believedthat Asian people, that is persons or humans of Asian extractions orancestry, such as Chinese, Japanese, Korean, and the like extraction orancestries, have increased eyelid tension relative to non-Asian people,that is persons or humans of non-Asian extraction or ancestry. Althoughthis is generally believed to be true, it should be noted that not allAsian persons have increased eyelid tension relative to all non-Asianpersons. A representative group of about 10 to about 15 Asian personshas a higher average eyelid tension relative to a representative groupof about 10 to about 15 non-Asian persons.

In another embodiment, contact lenses are provided including lens bodiesstructured to provide enhanced tear mixing in individuals who do nothave generally increased eyelid tensions. Advantageously, such lenseshave lens bodies that include a plurality of microchannels, as hereindisclosed, except that the microchannels are present in a lower density,that is fewer microchannels, than contact lenses configured for peoplewith increased eyelid tensions.

In another embodiment, the present contact lenses include lens bodiesstructured to provide enhanced tear mixing to individuals with palpebralaperture sizes that are associated with relatively thick PoLTF, such asAsian individuals. In additional embodiments, the present contact lensesinclude lens bodies that are structured to provide enhanced tear mixingto individuals with other anatomical characteristics, including, and notlimited to, eyelid characteristics that influence the ability of theeyelid to generate force on the eyeball during blinking, characteristicsof the tarsal plate (e.g., the size and/or thickness of the tarsalplate), eyelid thickness, the presence or absence of folds in theeyelid, aperture size, anterior ocular surface topography (e.g., cornealtopography, topography of the limbus, and topography of the corneallimbus and sclera), the positioning of the eyeball with respect to lid,and eyeball proptosis (e.g., the ability of the eyeball to move backwardwhen the eyelid blinks).

These contact lenses for a particular group of individuals aremanufactured using methods disclosed herein, and also including one ormore additional steps of designing the contact lenses to be structuredto provide enhanced tear mixing to the desired group of individuals,such as, individuals with certain eye and/or eyelid characteristics,which include eye shape, musculature, eyelid tension, and the like.Accordingly, contact lenses and methods of making contact lenses thatprovide enhanced tear mixing for particular or specific groups orpopulations of people are within the scope of the invention hereindisclosed.

The lenses of the present invention are preferably manufactured usingcomputerized lathing techniques. Alternatively, the lenses can bemanufactured by using any suitable conventional manufacturing techniqueor combination thereof. Many such techniques or processes areconventional and/or well known in the art. Such processes include, forexample, turning, laser-machining, swaging, injection moulding, casting(semi-mould, full mould) and the like and combinations thereof.

The contact lenses 10, 110, 210, 310 in accordance with the inventionare preferably flexible, soft silicone or hydrophilic silicone lenses orsoft lenses made from other hydrophilic materials, such as suitablehydrogel-forming polymeric materials and the like. However, withappropriate modifications, the present contact lenses may be “hard” or“rigid” lenses. The present contact lenses are particularly adapted forextended wear, for example, the lenses can be worn from about 1 day toabout 14 days or more without removal, or for disposable lenses.Materials which are suitable for use in the present lenses include,without limitation, conventional hydrogel materials, for example,hydroxyethyl methacrylate-based materials, silicone-hydrogel materials,gas permeable materials, lens materials described in Nicolson et al U.S.Pat. No. 5,849,811, other ophthalmically compatible lens materials, forexample, many of which are well known to those skilled in the art, andthe like and combinations thereof.

Preferably, the contact lenses 10, 110, 210 and 310, are of the presentinvention are produced by lathing the microchannels onto a toolinginsert that is subsequently used to produce a mold for the contact lensproduct. Hardware such as a variform attachment Fast tool servo on anOptiform lathe can be utilized to provide a tool insert with the desiredgeometry. For example, the tool servo can be programmed to lathe thetool insert in 24 semi-meridians (equi-spaced, 15 degrees apart) toproduce the lens shown in FIG. 1. The tool servo can be programmed usingknown techniques, for example using Minifiles, which is conventional andwell known by those of skill in the art, to describe the surface to belathed point by point. The tool servo can be additionally programmedsuch that both or either of the depth and width of the microchannels canbe varied. It is noted that the depth of the microchannel need not beconstant along its length, i.e. the channel could be made to get deeper,then shallower from the optic to the peripheral edge. The depth, widthand/or configuration of the microchannels may be varied frommicrochannel to microchannel. Of course, the microchannel depth at theedge of the lens cannot be deeper than the lens edge thickness.

The hardware for lathing the insert tool can be appropriately modifiedto cut up to about 384 meridians in order to allow for greaterflexibility in lens design.

The following non-limiting example shows the amount or relative degreeof tear mixing that occurs when the present lenses are worn on an eye incomparison to a conventional lens without microchannels.

EXAMPLE

Tear mixing under a soft contact lens can be estimated by measuring thetime required for a tracer material (e.g., dye, microspheres, red bloodcells or the like) to be removed from under the contact lens. Mosttear-mixing estimates are made using a fluorometer, which can measurethe change in fluorescence under a contact lens over a specified wearingperiod. Typically, either high-molecular-weight sodium fluorescein(Fluorosoft®, MW=600 Da) or a dye formulated as a fluorescein/dextrancombination (FITC-dextran, Smith Chemical; MW=1-12 kDa) is used in thefluorometric measurement. Fluorosoft® is absorbed by lenses with watercontents greater than about 50%. Therefore, preferably FITC-dextran(MW=9-12 kDa) is used to avoid underestimates of tear mixing that mightoccur with lens or ocular absorption of the tracer dye.

Two fluorometric methods are currently used to estimate tear mixing. Onetechnique uses a modified slit lamp with light focused on the PoLTF aschanges in fluorescence intensity (FI) are monitored. This technique hasthe advantage of placing an excitation light directly on the target area(e.g., tear film). An alternate fluorometric technique uses a scanningfluorometer (Ocumetrics, Inc., Mountain View, Calif.) that drives theexcitation light from the pre-lens tear film (PrLTF) to the cornea usinga computer-driven stepper motor. The instrument makes a series offluorescence-intensity readings and provides FI data centered around thepeak FITC-dextran fluorescence under the lens. This instrument is verysensitive to low levels of fluorescent dye. Unfortunately, since theplacement of the light cannot be controlled precisely, the tear-mixingestimate assumes that there is no fluorescence on the anterior lenssurface. This assumption is considered to be valid for lenses with slowtear-mixing rates but may not be accurate for lenses with efficient tearmixing. These instruments are conventional and details of eachinstrument are generally understood by those of skill in the art.

A procedure for estimating tear mixing is as follows: Baseline (B_(o))autofluorescence readings (cornea+lens) are obtained with the lens onthe eye of each subject. The lens is then removed, a small amount (e.g.,1 μl) of FITC-dextran is placed on the posterior lens surface, and thenthe lens is re-inserted directly onto the cornea. Next, the FI ismonitored for 30 minutes. Subjects are either allowed to blink at theirnormal rate or asked to blink at a rate of 15 blinks/min (average blinkrate) cadenced using a metronome. The rate of dye depletion isdetermined by fitting an exponential-decay model to the FI valuesobtained over the 30 minute observation period. After approximately 30minute, there is little or no detectable change in FITC-dextranintensity.

The exponential decay rate is expressed as a time constant, T, definedas the time required to deplete 37% of dye from under the lens per unitof time, T. For the computation, the first 5 minutes of data areeliminated because reflex tearing may occur as the lens is initiallyinserted. The efficiency of tear mixing is expressed as the timerequired to deplete 95% of the dye from under the lens, or 3T, which isdenoted as T₉₅. Advantageously, T₉₅ can be obtained immediately from thefluorescence-intensity decay data without further data manipulation. Theprocedure described above was performed in Dr. Kenneth Polse'slaboratory at the University of California, Berkeley.

Actual T₉₅ data obtained during experimentation on twenty-six patientswearing channeled lenses in accordance with the present invention,particularly, blended microchanneled lenses having 12 microchannels, at300 peak to peak, similar to contact lens 10 shown in FIGS. 1-3, and thesame twenty-six patients wearing substantially identical butnon-channeled lenses are shown in Table 1 and Table 2 below. TABLE 1Non-channeled Channeled lenses lenses T₉₅-c T₉₅-non ΔT₉₅ 25.33 45.5020.18 22.98 31.17 8.20 19.90 37.20 17.30 23.71 19.91 −3.80 20.66 29.498.82 20.52 23.27 2.75 22.35 35.80 13.45 33.84 23.45 −10.39 23.63 40.2816.64 25.32 33.83 8.51 28.73 43.11 14.38 23.25 29.29 6.04 25.82 31.685.86 Mean = 24.31 Mean = 32.61 Mean = 8.30p-value < 0.05

TABLE 2 Non-channeled Channeled lenses lenses T₉₅-c T₉₅-non ΔT₉₅ 21.9330.02 8.09 25.20 23.04 −2.16 28.59 21.13 −7.45 42.98 61.93 18.95 21.6221.70 0.09 25.51 23.29 −2.22 34.10 36.71 2.61 29.10 24.95 −4.15 33.8823.03 −10.84 28.40 30.51 2.11 49.47 41.50 −7.97 21.42 31.17 9.76 30.5630.2 −.36 Mean = 30.21 Mean = 30.71 Mean = 0.50p-value > 0.05

Table 1 represents data obtained from thirteen Asian patients, and table2 represents data obtained from thirteen non-Asian patients.

When the data are pooled, the mean T₉₅ for the channeled contact lensesis 27.26 minutes, and the mean T₉₅ for the non-channeled contact lensesis 31.66 minutes. The channeled lenses significantly increased the tearexchange rate, or reduced the tear exchange time (P<0.05). In otherwords, there was an overall change of approximately 14% in tear exchangetime, or an overall enhancement of tear exchange rate of approximately14%.

When the data from the seventeen patients (of the twenty-six patients)that showed decreased tear exchange times, or enhanced tear exchangerate, are examined, the mean T₉₅ for the channeled contact lenses is25.23 minutes, and the mean T₉₅ for the non-channeled contact lenses is34.86 minutes, resulting in an overall reduction in tear exchange timeof approximately 28%. The tear exchange rate was enhanced by at least0.4%, and was more typically enhanced by at least 6%. At least 45%improvements in tear exchange rate were also observed.

When the data from the patients who showed a decreased tear exchangetime are categorized into Asian and non-Asian patients, additionaldifferences in tear exchange rates for the Asian patients and non-Asianpatients are apparent. For example, the mean T₉₅ for the channeledcontact lenses for the Asian patients is 23.50 minutes and the mean T₉₅for the non-channeled contact lenses for the Asian patients is 34.60minutes, resulting in a difference of about 11.10 minutes, or about a26% change in tear exchange time. In comparison, the mean T₉₅ for thechanneled contact lenses for the non-Asian patients is 28.41 minutes,and the mean T₉₅ for the non-channeled contact lenses for the non-Asianpatients is 35.34 minutes, resulting in a difference of about 6.94minutes, or about a 20% change in tear exchange time.

In addition, the data demonstrate that the contact lenses used in thisexample provided enhanced tear mixing to a greater percentage of Asianpeople (approximately 85%) compared to the non-Asian people(approximately 46%).

Thus, the above data confirm that the lenses herein disclosed providesubstantial advantages over lens without channels in terms of enhancedtear exchange. In addition, the data confirm that certain lensconfigurations may be preferred for different individuals or populationsof people who have particular eye and/or eyelid anatomical andphysiological features. In other words, lenses with one configuration ofmicrochannels may exhibit improved tear exchange rates for Asiansubjects, and lenses with a different configuration of microchannels,such as decreased channel density or greater distances between apices ofmicrochannels, may exhibit improved tear exchange rates for non-Asiansubjects.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

1. A silicone hydrogel contact lens, comprising: a silicone hydrogellens body having a posterior face and an anterior face; and a pluralityof microchannels defined in the posterior face of the lens body anddefining a substantially continuous wave form circumferentially, thelens body being structured to reduce the time to exchange 95% of tearfluid by at least about 5% when the contact lens is worn on an eyerelative to a substantially identical contact lens without a pluralityof microchannels.
 2. The silicone hydrogel contact lens of claim 1,wherein the lens body is structured to reduce the time to exchange 95%of tear fluid by at least about 15% when the contact lens is worn on theeye relative to a substantially identical contact lens without aplurality of microchannels.
 3. The silicone hydrogel contact lens ofclaim 1, wherein each microchannel of the plurality of microchannelsdefines a waveform circumferentially.
 4. The silicone hydrogel contactlens of claim 1, wherein each microchannel of the plurality ofmicrochannels defines a substantially junctionless waveformcircumferentially.
 5. The silicone hydrogel contact lens of claim 1,wherein the plurality of microchannels defines a substantiallycontinuous, substantially junctionless waveform circumferentially. 6.The silicone hydrogel contact lens of claim 1, wherein each of themicrochannels comprises a microchannel which is substantiallyjunctionless along at least a portion of a length of the microchannel.7. The silicone hydrogel contact lens of claim 1, wherein the lens bodyincludes an optical zone which is substantially free of the plurality ofmicrochannels.
 8. The silicone hydrogel contact lens of claim 1, whereinthe plurality of microchannels comprises about 3 to about 200microchannels.
 9. The silicone hydrogel contact lens of claim 1, whereinthe lens body is structured to provide enhanced tear mixing of post lenstear film of a person of a desired group of people when worn on an eyeof the person relative to a substantially identical contact lens worn byanother person of a different group of people.
 10. The silicone hydrogelcontact lens of claim 9, wherein the lens body is structured to provideenhanced tear mixing of post-lens tear film of a person of a group ofpeople who have eye or eyelid characteristics specific for the group ofpeople.
 11. The silicone hydrogel contact lens of claim 9, wherein thelens body is structured to enhance tear mixing of post-lens tear filmwhen the contact lens is worn on the eye of an Asian person relative totear mixing of post-lens tear film provided by an identically structuredlens worn on the eye of a non-Asian person.
 12. A silicone hydrogelcontact lens comprising: a silicone hydrogel lens body having aposterior face, and an anterior face, a thickness defined as thedistance between the posterior face and the anterior face, and aplurality of radially extending microchannels defined in the posteriorface of the lens body and having a depth less than about 90% of thethickness and a maximum width less than about 500 microns, themicrochannels sized and adapted to promote effective tear fluid exchangebetween an exposed surface of the eye and a surface of the eye coveredby the lens body.
 13. The silicone hydrogel contact lens of claim 12,wherein the lens body is structured to reduce the time to exchange 95%of tear fluid by at least about 5% when the contact lens is worn on theeye relative to a substantially identical contact lens without aplurality of microchannels.
 14. The silicone hydrogel contact lens ofclaim 12, wherein the lens body is structured to reduce the time toexchange 95% of tear fluid by at least about 35% when the contact lensis worn on the eye relative to a substantially identical contact lenswithout a plurality of microchannels.
 15. The silicone hydrogel contactlens of claim 12, wherein each of the microchannels includes a curvedsurface and wherein the curved surface of each microchannel issubstantially continuously curved circumferentially.
 16. The siliconehydrogel contact lens of claim 12, wherein each of the microchannels issubstantially junctionless along a portion of a length of themicrochannel.
 17. The silicone hydrogel contact lens of claim 12, whichincludes an optical zone which is substantially free of the plurality ofmicrochannels.
 18. The silicone hydrogel contact lens of claim 12,wherein the lens body is structured to provide enhanced tear mixing ofpost lens tear film of a person of a desired group of people when wornon an eye of the person relative to a substantially identical contactlens worn by another person of a different group of people.
 19. Thesilicone hydrogel contact lens of claim 12, wherein the lens body isstructured to provide enhanced tear mixing of post-lens tear film of aperson of a group of people who have eye or eyelid characteristicsspecific for the group of people.
 20. The silicone hydrogel contact lensof claim 12, wherein the lens body is structured to enhance tear mixingof put-lens tear film when the contact lens is worn on an eye of anAsian person relative to tear mixing of post-lens tear film provided byan identically structured contact lens worn on an eye of a non-Asianperson.
 21. A silicone hydrogel contact lens comprising: a siliconehydrogel lens body having a posterior face, an anterior face, and athickness defined as the distance between the posterior face and theanterior face, and a plurality of radially extending microchannelsdefined in the posterior face of the lens body and having a depth lessthan about 90% of the thickness and a maximum width less than about 500microns.
 22. The silicone hydrogel contact lens of claim 21, wherein thelens body comprises from about 3 to about 200 microchannels.
 23. Thesilicone hydrogel contact lens of claim 21, wherein the lens bodycomprises from about 10 to about 100 microchannels.
 24. The siliconehydrogel contact lens of claim 21, wherein each of the microchannels hasa decreasing taper toward an optical axis of the lens body.
 25. Thesilicone hydrogel contact lens of claim 21, wherein each of themicrochannels has a maximum width adjacent a peripheral edge of the lensbody.
 26. The silicone hydrogel contact lens of claim 21, wherein thedepth of the microchannels is less than about 80% of the thickness ofthe lens body.
 27. The silicone hydrogel contact lens of claim 21,wherein the depth of the microchannels is from about 0.1 microns toabout 50 microns.